(i) Field of the Invention
This invention relates to a novel metal-working oil composition, and more specifically to a metal-working oil composition which contains a lube-oil component and a polymer compound of a homopolymer of acrylic amide or a copolymer of acrylic amide and another monomer or a salt of the polymer compound.
(ii) Description of the Prior Art
Conventional metal-working oils which have generally been used are each obtained by adding lube-oil additives such as an oiliness agent, extreme-pressure additive, rust preventive and/or antioxidant to a lube-oil component such as an oil, fat, mineral oil or fatty acid ester and then converting the resultant mixture into an o/w-type emulsion by means of an emulsifier. They are fed to metal-working parts, usually with concentrations of 1 to 20%. In the case of rolling a metal for example, it has been attempted to increase the rolling speed so as to achieve mass production, relying upon rapid advancement in rolling facilities and technology which has been achieved in recent years. Reflecting such an attempt, requirements for rolling oil such as circulation stability of lube-oil, working efficiency and treatment readiness of waste water have become progressively severer. There is thus a strong standing desire for the development of a rolling oil which can satisfactorily meet such requirements. However, conventional rolling oils which make use of emulsifiers are accompanied by various drawbacks and are hence unable to fulfill such requirements. In the case of a conventional rolling oil relying upon an emulsifier, the rolling lubricity was controlled by changing the type and amount of the emulsifier in such a way that the amount of the oil which was to adhere on rolls and each coil surfaces, in other words, the plate-out quantity was either increased or decreased. In such an emulsifier-containing rolling oil as described above, its plate-out quantity and the stability of emulsion however show mutually-contradictory tendency. Namely, the plate-out quantity on rolls and coil surfaces is decreased and the lubricity is thus rendered insufficient if the stability of the emulsion is enhanced. If one tries to increase the plate-out quantity, the emulsion becomes unstable and develops various problems when re-circulated. Accordingly, conventional rolling oils making use of emulsifiers and accompanied by such drawbacks as mentioned above. Furthermore, still further improvements are also desired to the lubricity and working efficiency of other metal-working oils such as press-working oils and cutting oils.
The present inventors therefore carried out a research with a view toward solving the aforementioned drawbacks which conventional emulsion-type metal-working oils had. As a result, it was succeeded to improve the above-described drawbacks by using a lube-oil component, which contained an oil, fat or wax having a melting point of 20.degree. to 100.degree. C., in combination with a specific hydrophilic dispersant (a water-soluble, anionic, polymer compound) in such a way that the lube-oil component was stably suspended and dispersed in a solid form in water at a temperature below the melting point but the resultant dispersion became unstable when fed to each working part, i.e., at a temperature above the melting point. A patent application has been already made on the above finding (see, Japanese Patent Application Laid-open No. 147593/1980).